1. Field of the Invention
The present invention relates to rotary actuators that output a driving torque as a result of output shafts pivoting in a rotational direction due to an action of a pressure medium.
2. Description of Related Art
A rotary actuator having such a configuration as one disclosed in U.S. Pat. No. 5,601,165 is known as one of the rotary actuators that output a driving torque as a result of output shafts pivoting in a rotational direction due to an action of a pressure fluid serving as a pressure medium.
In the rotary actuator disclosed in U.S. Pat. No. 5,601,165, ribs are provided inside a cylinder as an integral unit, and vanes are provided to an output shaft that is rotatably installed inside the cylinder. Both ends of the cylinder are provided with end caps. The ribs and the inner wall surface of the cylinder, as well as the vanes and the outer wall surface of the output shaft form pressure chambers. Adjacent pressure chambers are alternately supplied with a pressure fluid, the output shaft thereby pivots in a rotational direction due to an action of the pressure fluid, and, as a result, a driving torque is output.
In the above rotary actuator, seals that are formed in a plate shape or in a block shape are inserted in grooves provided on the ribs and the vanes. The seals inserted in the ribs are pressed against the outer wall surface of the output shaft, and the seals inserted in the vanes are pressed against the inner wall surface of the cylinder. Thus, the adjacent pressure chambers are sealed against each other. The pressure chambers are also sealed against each other by means of gaskets between the end caps and the output shaft, as well as between the end caps and the vanes.